Images of Inundation: Day Four at the World Water Forum in Istanbul

Perhaps it was just the rain pouring down outside the conference hall windows, but issues related to floods conjured up particularly vivid images at the 5th World Water Forum today. While the planet as a whole faces an ever-more-acute water shortage, cities and regions struggling to deal with an often-seasonal excess of water can hardly be expected to feel blessed.

Washed AwayA slideshow presentation by Jesper G. Dannisoe of the Danish company DSI showed some of the worst-case scenarios of urban flooding in the developing world: solid waste swept into the streets from overloaded sewage and stormwater systems, elevated homes submerged up to their doors, forcing residents to walk or swim through the contaminated water that is also seeping into the tanks where they stored household water, and sometimes even into the city's main water supply itself.

According to the 2007 Intergovernmental Panel on Climate Change report, more than two-thirds of large cities -- containing millions of people -- are vulnerable to rising sea levels. Increasingly heavy storms associated with global warming can also overwhelm city infrastructure. A computer-modeling program, MIKE FLOOD, by DHI is meant to help cities better prepare for inundation by showing in detail where flood waters are likely to go, which buildings are most vulnerable to damage, and estimating the costs that will be incurred.

Coastal ConnectionsThe effort to better mitigate the safety, health, and economic risks associated with floods has also brought coastal cities from New York to Jakarta, London to Sao Paolo, together in the Connecting Delta Cities project, part of President Bill Clinton's C40 initiative for cities to tackle climate change. Though representatives at the water forum emphasized that different delta cities need different solutions because of their varying socioeconomic situations, they hope to find benefit in exchanging information and knowledge about the problems they share -- problems that will soon affect half the world's population.

London, for example, is looking at adopting both the Dutch technique of setting aside land that occasionally floods for compatible uses, like parks and floating greenhouses, and the permeable pavement used in Seattle to better absorb stormwater runoff. Singapore, meanwhile, is working with a Dutch research institute on dike construction. After all, when the climate is changing this fast, there's really no time to start from scratch.